[llvm-cxxfilt] De-emphasize "function" in llvm-cxxfilt docs and --help (#113309)
llvm-cxxfilt can demangle names of data symbols, in addition to function
names.
$ llvm-cxxfilt _ZN6garden5gnomeE
garden::gnome
And type names too, on request:
$ llvm-cxxfilt -t i
int
Update some overly specific the wording in the --help and documentation
that suggests otherwise.